The present invention relates to an electrical pressure transducer which detects a fluid pressure and produces an electrical signal representing the pressure, and more specifically to a pressure transducer having a reference pressure chamber formed inside a sensor chip.
FIG. 12 shows one conventional pressure sensor (as disclosed in Japanese patent provisional publication No. 58-63826).
The device of FIG. 12 is an absolute pressure measurement type. A pressure sensor chip 1 is bonded through an adhesive layer 7 onto a pedestal 4, which is in turn, bonded through another adhesive layer 8 onto a stem member 5. The sensor chip 1 is connected through lead wire 2 to lead pins 3, and enclosed in a vacuum reference chamber 10, which is formed by hermetically joining a cap 6 onto the stem member 5 by welding or soldering, and sealing a hole 12 of the cap 6 by a solder 9 in a vacuum. A measurand pressure to be measured is applied to the bottom of the sensor chip 1 through a bore of a tubular portion 11 of the stem member 5 and a bore of the pedestal 4.
However, this conventional pressure sensor is disadvantageous in that it is necessary to form the hermetically sealed vacuum reference chamber 10 in the sensor housing, and accordingly it requires a large expenditure to package the sensor chip 1 in the sensor housing. Besides, care must be directed to selection of materials of the pedestal 4, and the adhesive layers 7 and 8 in order to reduce thermal stresses due to difference in thermal expansion coefficient between the sensor chip 1 and the stem member 5.